When you start a string literal with ' (single-quotes), you're creating a verbatim string - that is, every character inside the string is interpreted literally and variable references and expressions won't expand!
Use " if you want the variable to be expanded:
$var = 'C:'
Get-WmiObject -Class win32_logicaldisk -Filter "DeviceID='$var'"
If your variable name has weird characters, or is followed by a word character, you can qualify the variable name with curly brackets {} immediately after the $:
$var = 'C:'
Get-WmiObject -Class win32_logicaldisk -Filter "DeviceID='${var}'"
How to expand variable in powershell? - Stack Overflow
powershell - %temp% etc not working - Stack Overflow
windows - Set nested expandable environment variable with PowerShell - Stack Overflow
Environment Variable inside a single '
How to set an environment variable using PowerShell?
To set an environment variable, you can use the following syntax.
$Env:VariableName = “Value”
Replace VariableName with the desired name of your variable and Value with the value you want to assign to it, as example below.
$Env:MY_VAR = “MyValue”
How to check if an environment variable exists in PowerShell?
To check if a specific environment variable exists, you can use the following command.
Test-Path Env:MY_VAR Replace MY_VAR with the name of the environment variable you want to check. If the variable exists, it will return True; if not, it will return False.
How do I list all variables in PowerShell?
To list all variables in your PowerShell session, you can use:
Get-ChildItem Env:
This command will show all currently defined variables in the session, including environment variables.
I was trying to add a environment variable to my user's Path using PowerShell, so I searched about and ended up with a code similar to this one:
[Environment]::SetEnvironmentVariable("TEST_VAR", "test-value", "User")
$currPath = [Environment]::GetEnvironmentVariable("Path", "User")
$newPath = "$currPath;%TEST_VAR%;"
[Environment]::SetEnvironmentVariable("Path", $newPath, "User")
The idea is to change TEST_VAR value in the future and by doing so updating the Path easily.
The problem I've found is that when setting Path with a non-expanded variable (in this case, %TEST_VAR%) it won't expand automatically. So, if I open the cmd and try to echo Path, I get something like this:
C:\Progr [...] omeOherStuff;%TEST_VAR%;
When it should be returning this:
C:\Progr [...] omeOherStuff;test-value;
Some places where I searched said that the answer to this problem is messing around with reg add, but I am not sure about it and even with some testing trying to set %TEST_VAR% as REG_EXPAND_SZ didn't work for me.
That is my first post here, also sorry if my english is bad. Thanks.
When you start a string literal with ' (single-quotes), you're creating a verbatim string - that is, every character inside the string is interpreted literally and variable references and expressions won't expand!
Use " if you want the variable to be expanded:
$var = 'C:'
Get-WmiObject -Class win32_logicaldisk -Filter "DeviceID='$var'"
If your variable name has weird characters, or is followed by a word character, you can qualify the variable name with curly brackets {} immediately after the $:
$var = 'C:'
Get-WmiObject -Class win32_logicaldisk -Filter "DeviceID='${var}'"
If, for instance, you're getting data from a file with select-string, the return is a single quote string. If that string contains variables they won't expand. Invoke-Expression can be used if the variable is clean - not mixed in with other text:
a = '
a -> 123
If the variable is part of a path name, this doesn't work. Use $ExecutionContext.InvokeCommand.ExpandString($var)
$path = '$Home/HiMum'
$ExecutionContext.InvokeCommand.ExpandString($path)
-> /home/JoeBlogs/HiMum
You lucky sods on Windows might be able to use Convert-String to change singles to doubles.
If you are executing that line from PowerShell rather than from CMD, you can use the PowerShell environment variable syntax:
PS C:\> & "$env:SystemRoot\System32\WindowsPowerShell\v1.0\powershell.exe"
You can use [Environment]::ExpandEnvironmentVariables to expand environment variables within a string the old-fashioned way.
$s = '%systemroot%\temp'
[Environment]::ExpandEnvironmentVariables($s)
Hi Everyone,
I am not great with scripting, so apologies for not using the correct terminology and likely asking a very basic question. I am attempting to install an MSI package and my MSI package has a space in the name (I can't rename it, it has to be this name). I am invoking the start-process command with the below argument list.
-ArgumentList '/I "$env:temp\My MSI File.msi" /qn'
This fails and I believe it is due to the use of the single quote which I think it turning everything inside of it as a literal statement so it is not reading the environment variable etc. What do I need to do to get this to work?
Cheers!
***Edit, I figured it out. I needed to wrap what needed to be in quotes with an extra set of quotes and use quotes around the entire argument list like this:
-ArgumentList "/I ""$env:temp\My MSI File.msi"" /qn"
If sometime during a PowerShell session you need to see or to temporarily modify the PATH environment variable, you can type one of these commands:
Copy$env:Path # shows the actual content
$env:Path = 'C:\foo;' + $env:Path # attach to the beginning
$env:Path += ';C:\foo' # attach to the end
Changing the actual environment variables can be done by
using the env: namespace / drive information. For example, this
code will update the path environment variable:
Copy$env:PATH = "SomeRandomPath"; (replaces existing path)
$env:PATH += ";SomeRandomPath" (appends to existing path)
Making change permanent
There are ways to make environment settings permanent, but if you are only using them from PowerShell, it's probably a lot better to use Powershell profiles script.
Everytime a new instance of Powershell starts, it look for specific script files (named profile files) and execute them if they do exist. You can edit one of these profile to customize your enviroment.
To know where those profile scripts are located in your computer type:
Copy$profile
$profile.AllUsersAllHosts
$profile.AllUsersCurrentHost
$profile.CurrentUserAllHosts
$profile.CurrentUserCurrentHost
You can edit one of them, for example, by typing:
Copynotepad $profile